package com.example.works;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.util.DisplayMetrics;
import android.view.View;

import java.util.ArrayList;
import java.util.Random;

public class TheScreenView extends View {
    //界面主线程的控制变量
    private boolean drawing = false;
    //储存当前已有的球的信息
    private ArrayList<Circle> circles;
    private Paint mPaint;
    //球的运动范围
    public int WIDTH;
    public int HEIGHT;
    public static final double PI = 3.14159265;
    Paint mPaint2 = new Paint();
    public TheScreenView(Context context) {
        super(context);
        circles = new ArrayList<Circle>();
        //加入了两个球
        circles.add(new Circle());
        circles.add(new Circle());
        circles.add(new Circle());
        circles.add(new Circle());
        circles.add(new Circle());

        mPaint = new Paint();
        mPaint.setColor(Color.YELLOW);
        mPaint.setAntiAlias(true);
        mPaint2.setStyle(Style.FILL);
        mPaint2.setColor(Color.RED);
        mPaint2.setAntiAlias(true);
        DisplayMetrics dm = new DisplayMetrics();
        ((Activity) context).getWindowManager().getDefaultDisplay().getMetrics(dm);
        WIDTH  = dm.widthPixels;
        HEIGHT = dm.heightPixels;

        //启动界面线程,开始自动更新界面
        drawing = true;
        new Thread(mRunnable).start();
    }
    private Runnable mRunnable = new Runnable() {
        //界面的主线程
        @Override
        public void run() {
            while( drawing )
            {
                try {
                    //更新球的位置信息
                    update();
                    //通知系统更新界面,相当于调用了onDraw函数
                    postInvalidate();
                    //界面更新的频率,这里是每30ms更新一次界面
                    Thread.sleep(30);
                    //Log.e(TAG, "drawing");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    };
    public void stopDrawing()
    {
        drawing = false;
    }
    @Override
    public void onDraw(Canvas canvas)
    {
        //在canvas上绘制边框
        canvas.drawRect(0, 0, WIDTH, HEIGHT, mPaint2);
        //在canvas上绘制球
        for( Circle circle : circles) {
            canvas.drawCircle(circle.x, circle.y, circle.radius, mPaint);
        }
    }
    //界面的逻辑函数,主要检查球是否发生碰撞,以及更新球的位置
    private void update(){
        if( circles.size()>1) {
            for( int i1=0; i1<circles.size()-1; i1++)  {
                //当两个球发生碰撞,交换两个球的角度值
                for( int i2=i1+1; i2<circles.size(); i2++){
                    if( checkBumb(circles.get(i1),circles.get(i2))){
                        circles.get(i1).changeDerection(circles.get(i2));
                    }
                }
            }
        }
        //更新球的位置
        for( Circle circle: circles){
            circle.updateLocate();
        }
    }
    private boolean checkBumb(Circle c1, Circle c2) {
        return (c1.x-c2.x)*(c1.x-c2.x) + (c1.y-c2.y)*(c1.y-c2.y) <= (c1.radius+c2.radius)*(c1.radius+c2.radius);
    }
    /**
     * 自定义的View的内部类,存储每一个球的信息
     */
    class Circle {
        float x= 30+30*(new Random().nextFloat())*10;
        float y= 50+170*(new Random().nextFloat());
        double angle= (new Random().nextFloat())*2*PI;
        int speed=20;
        float radius=40+20*(new Random().nextFloat());
        public Circle() {
        }
        public Circle( float x, float y, int r ){
            this.x = x;
            this.y = y;
            radius = r;
        }
        //利用三角函数计算出球的新位置值,当与边界发生碰撞时,改变球的角度
        public void updateLocate()   {
            x = x+ (float)(speed *Math.cos(angle));
            //Log.v(TAG, Math.cos(angle)+"");
            y = y+ (float)(speed *Math.sin(angle));
            //Log.v(TAG, Math.cos(angle)+"");
            if( (x+radius)>=WIDTH )    {
                if( angle >=0 && angle <= (PI/2))
                    angle = PI - angle;
                if( angle > 1.5 * PI && angle <= 2*PI)
                    angle = 3 * PI - angle;
            }
            if( x-radius <=0 )   {
                if( angle >= PI && angle <= 1.5*PI )
                    angle = 3*PI - angle;
                if( angle >= PI/2 && angle < PI)
                    angle = PI - angle;
            }
            if( y-radius<=0 || y+radius>=HEIGHT)
                angle = 2*PI - angle;
        }
        //两球交换角度
        public void changeDerection(Circle other)  {
            double temp = this.angle;
            this.angle = other.angle;
            other.angle = temp;
        }
    }
}